Kinematic alignment is bone and soft tissue preserving compared to mechanical alignment in total knee arthroplasty

Abstract

Background: Kinematically aligned (KA) total knee arthroplasty (TKA) has emerged as an alternative approach to the intraoperative alignment targets of mechanically aligned (MA) TKA. While the clinical outcomes of the two philosophies have been investigated, further investigation is required to quantify exactly how the two philosophies differ in their approach to correcting the deformities encountered in osteoarthritic knees such as fixed flexion deformities (FFD) and coronal malalignment. The aim of this paper was to compare MA and KA philosophies in TKA in terms of the intra-operative correction of FFD and coronal malalignment and quantify the way in which each philosophy achieves a well-balanced knee that can reach full extension. Methods: A retrospective review of prospective data collected from 210 consecutive TKAs performed by a single surgeon between March 2015 and May 2017 was undertaken. MA and KA cases were compared in terms of pre-operative patient deformity and characteristics, intraoperative steps taken to correct FFD (including bony resections, soft tissue releases and components used) and postoperative alignment achieved. Results: One hundred twenty MA and 90 KA TKAs were analysed. There was no significant difference in terms of patient age, gender and preoperative coronal and sagittal deformity between the two cohorts. KA TKAs were able to achieve the same degree of sagittal correction as MA TKAs with less total bony resection (16.7 mm vs. 18.9 mm, p b 0.0001), less soft tissue releases (10% vs. 49.2%, p b 0.0001). This was achieved with a difference in component alignment. The femur was in more valgus (−2.5 vs. −0.03°, p b 0.0001), the tibia in more varus (2.3 vs. 0.3°, p b 0.0001), and the overall alignment slightly more varus in the KA group (1.1 vs. 0.4°, p = 0.007), without significant difference in the proportion of patients within three degrees of a neutral axis. Conclusion: This study shows that using a kinematic alignment philosophy in total knee arthroplasty results in the achievement of extension range-of-motion and soft tissue balance goals with less bone resection and less soft tissue release. This allows for bone stock preservation and minimization of trauma due to soft tissue release. Further study is required to correlate these results with patient reported outcomes and determine their clinical significance. Level of evidence: IIIretrospective cohort study.

Clinical outcomes of kinematic alignment versus mechanical alignment in total knee arthroplasty: a systematic review

“…Twenty-three clinical articles were analysed, including two meta-analyses, 39 , 40 one systematic review, 41 eight RCTs, 11 , 42 – 48 six case control studies, 30 , 33 , 36 , 49 – 51 and six case series 29 , 31 , 32 , 34 , 52 , 53 (six level I, four level II, seven level III, and five level IV). Fifteen original research papers reporting clinical results and survivorship were included in the systematic review, summarized in Table 1 and Table 2 .…”

“… 27 , 28 Proponents of KA believe that this strategy may require less soft tissue release, preserve bone, reduce post-operative pain, and improve post-operative function, thereby reducing the proportion of patients who remain discontent following TKA. 29 , 36 …”

How joint line orientation affects the amount of bone resection in mechanically aligned TKA: a retrospective clinical-radiographic correlation study

“…In contrast with patients who receive primary total hip arthroplasty, approximately 20% of those who receive TKA are not satis ed with their outcomes (11,12). Although its underlying reason is not clear, alignment technique of TKA is beginning to be considered to be related to the patient's postoperative outcomes and dissatisfaction (13,14). With the application of more accurate alignment assistant instruments, the conventional MA technique has begun to be challenged in recent years (7,15,16), because MA cannot fully respect the patient's natural alignment of lower extremities and joint line orientation, and a signi cant variation in overall coronal limb alignment and in femoral and tibial joint lines had been proved to exist in osteoarthritic knees (17).…”

Kinematically Aligned TKA Aligns the Ankle Joint Line Closer to Those of the Native Ankle than Mechanically Aligned TKA in Bipedal Stance

“…However, the mechanism for restoration of ankle joint alignment with KATKA is not clear yet. It is possible that the KATKA balances the soft tissue tension around the ankle joint by minimizing soft tissue release and horizontalizing tibial plateau, 1,16,24 but further study is warranted to increase understanding. In a previous study, intentional varus alignment was applied to the long-standing severe varus knee arthritis group 12 due to concerns that acute correction of long-standing varus alignment of knee joints would lead to the overcorrection in the alignment of the ankle joint line.…”